Among power conditioning systems with a fuel cell, a power conditioning system is known which can supply output power of a fuel cell to a load by supplying fuel gas (e.g. hydrogen) and oxidant gas (e.g. air) to the fuel cell according to a request of the load connected to the fuel cell.
In the power conditioning system as described above, to control an operating state of the fuel cell, alternating-current components of an output current and an output voltage of the fuel cell are measured while an alternating-current voltage signal is output, for example, by an impedance measuring device, a controller and the like, and an internal impedance of the fuel cell is estimated by computing these measured alternating-current components.
WO2012/077450 discloses an internal resistance measuring device for measuring an internal resistance (internal impedance) of a laminated battery in which a plurality of power generation elements are laminated. In this internal resistance measuring device, the internal resistance of the laminated battery is measured on the basis of potential differences between potentials on positive and negative electrode sides of the laminated battery and a potential on a part between the positive and negative electrode sides.
However, although a travel motor or the like is illustrated as a load device of the device, no specific configuration is disclosed in WO2012/077450. Here, the present applicant proposes a fuel cell system (power condition system) with a battery (high-voltage secondary battery) and a fuel cell provided electrically in parallel to the battery.
In a power condition system in which a battery and a fuel cell are arranged in parallel, a DC/DC converter is provided at least on an output side of either one of the battery and the fuel cell to link (synchronize) an output of the battery and an output of the fuel cell. It is considered to utilize the internal resistance measuring device as described above to measure an impedance of the fuel cell in such a power condition system.